1. Field of the Invention
The present invention relates generally to x-ray imaging systems, for example, cardiac or peripheral angiographic systems. More particularly, the present invention is directed to a method and system for reducing bright burn in x-ray images.
2. Background Discussion
Radiography is the use of certain spectra of electromagnetic radiation, usually x-rays, to image a human body. Angiography, a particular radiographic method, is the study of blood vessels using x-rays. An angiogram uses a radiopaque substance, or contrast medium, to make the blood vessels visible under x-ray. Angiography is used to detect abnormalities, including narrowing (stenosis) or blockages (occlusions), in the blood vessels throughout the circulatory system and in certain organs.
Cardiac angiography, also known as coronary angiography, is a type of angiographic procedure in which the contrast medium is injected into one of the arteries of the heart, in order to view blood flow through the heart, and to detect obstruction in the coronary arteries, which can lead to a heart attack.
Peripheral angiography, in contrast, is an examination of the peripheral arteries in the body; that is, arteries other than the coronary arteries. The peripheral arteries typically supply blood to the brain, the kidneys, and the legs. Peripheral angiograms are most often performed in order to examine the arteries which supply blood to the head and neck, or the abdomen and legs.
A drawback in cardiac, and especially peripheral, angiography, and considered a nuisance by physicians, is bright image artifacts, such as spurious images, unintended splotches, and other aberrant perturbations that appear on the x-ray image. The term “bright burn” is often used to refer to an image artifact in which a particular region of an image appears relatively bright. Bright burn can greatly diminish the quality of imaging in areas with little or no x-ray absorption, such as the lung area or the legs. The low x-ray absorption generates very high signals, and hence bright areas, which can distract the physician, or technician, from his or her diagnostic or interventional procedure.
Several areas of the body are particularly problematic to image degradation because of bright burn. For example, imagining the lung area, the legs, or any portion of the human body with large areas of empty space, can generate images with areas with significant bright burn.
Conventional attempts to solve the problems associated with bright burn include manually moving wedge-shaped filters into areas of bright burn to partially block x-ray radiation, or using dynamic range compression algorithms on the raw image data to reduce bright burn.
Both of these solutions have drawbacks. For example, the process of manually moving wedge filters hampers and impedes an operator's workflow. Additionally, after a change of angulation, the wedge filter may no longer be necessary; if the operator forgets to take the filter out of the x-ray beam, the filter will actually diminish image quality.
Furthermore, a drawback to dynamic range compression algorithms is that they require very high compression ratios to effectively compensate for bright burn artifacts. Since such algorithms are not discriminative, but operate on the entire image, actual areas of interest (for example, the arteries in the heart or the legs, and the surrounding anatomy) may be altered in undesired ways.
Thus, conventional x-ray images may suffer from bright burn areas that degrade the image quality and impede the ability to easily comprehend the contents of the x-ray images.
Therefore, it would be an advancement in the state of the art to provide systems and methods that reduce bright burn in x-ray images.